Fix for iOS builder.

Change-Id: I5b6c977b187446c848182a9294d5bed6b5f9f6e4
Reviewed-on: https://go-review.googlesource.com/16633
Run-TryBot: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>